include/asm-arm/mmu_context.h

   1 /*
   2  *  linux/include/asm-arm/mmu_context.h
   3  *
   4  *  Copyright (C) 1996 Russell King.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  Changelog:
  11  *   27-06-1996 RMK     Created
  12  */
  13 #ifndef __ASM_ARM_MMU_CONTEXT_H
  14 #define __ASM_ARM_MMU_CONTEXT_H
  15
  16 #include <asm/proc-fns.h>
  17
  18 #if __LINUX_ARM_ARCH__ >= 6
  19
  20 /*
  21  * On ARMv6, we have the following structure in the Context ID:
  22  *
  23  * 31                         7          0
  24  * +-------------------------+-----------+
  25  * |      process ID         |   ASID    |
  26  * +-------------------------+-----------+
  27  * |              context ID             |
  28  * +-------------------------------------+
  29  *
  30  * The ASID is used to tag entries in the CPU caches and TLBs.
  31  * The context ID is used by debuggers and trace logic, and
  32  * should be unique within all running processes.
  33  */
  34 #define ASID_BITS       8
  35 #define ASID_MASK       ((~0) << ASID_BITS)
  36
  37 extern unsigned int cpu_last_asid;
  38
  39 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
  40 void __new_context(struct mm_struct *mm);
  41
  42 static inline void check_context(struct mm_struct *mm)
  43 {
  44         if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
  45                 __new_context(mm);
  46 }
  47
  48 #define init_new_context(tsk,mm)        (__init_new_context(tsk,mm),0)
  49
  50 #else
  51
  52 #define check_context(mm)               do { } while (0)
  53 #define init_new_context(tsk,mm)        0
  54
  55 #endif
  56
  57 #define destroy_context(mm)             do { } while(0)
  58
  59 /*
  60  * This is called when "tsk" is about to enter lazy TLB mode.
  61  *
  62  * mm:  describes the currently active mm context
  63  * tsk: task which is entering lazy tlb
  64  * cpu: cpu number which is entering lazy tlb
  65  *
  66  * tsk->mm will be NULL
  67  */
  68 static inline void
  69 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  70 {
  71 }
  72
  73 /*
  74  * This is the actual mm switch as far as the scheduler
  75  * is concerned.  No registers are touched.  We avoid
  76  * calling the CPU specific function when the mm hasn't
  77  * actually changed.
  78  */
  79 static inline void
  80 switch_mm(struct mm_struct *prev, struct mm_struct *next,
  81           struct task_struct *tsk)
  82 {
  83         unsigned int cpu = smp_processor_id();
  84
  85         if (prev != next) {
  86                 cpu_set(cpu, next->cpu_vm_mask);
  87                 check_context(next);
  88                 cpu_switch_mm(next->pgd, next);
  89                 cpu_clear(cpu, prev->cpu_vm_mask);
  90         }
  91 }
  92
  93 #define deactivate_mm(tsk,mm)   do { } while (0)
  94 #define activate_mm(prev,next)  switch_mm(prev, next, NULL)
  95
  96 #endif